Flash lamp



M. PIPKIN FLASH LAMP Dec. 29, 1942.

Filed Feb. 26, 1940 lnvenror:

Marvin Pipkin,

Peleriied Dec. 29, ieee eeeeeee ruse Moo Mervin Hem, @levelcml Heights, @lolo, oselcmor lo @eroeml Electric eomoimv, c. eomoeefsioii oi New Flori";

.liioilcellom Fekruorr 2o, Elli iii, Seriiil No. wefilll ((Cl. 67 m) eni, have been provided, in practically all coees,

with bulbs similar iii shape to the conventional pEfiL-SIZEZJGQ bulb employee :Kor electric incanmgos. While such peer-showed loullos ole ior lrlcemleeeerr'e lamps, they preiii ellsoeiveiiieeee lleii used for flash romeo. Thus; the reverse olilveel portions ioirbice; the bulbous XEOEMQH to oiilio neck is a. source of weakness in IGEQK ShEJGfi-fl bulbs when used. for flash lorries, end Toulo strength is an momma consideration in flesh lamps where considerable intemol pressure is flevelooeii when the lamp is fleshed. This vieolziiees of pearshaped ioclloe therefore pieces a. Elicitation u'pon the-amount of the loading or llglia givirig charge which can be safely introduced into the bulb. Anoiherolseolvenioge coririec'zecl with the use of 338ET=S11W61 bulbs for fiaslrlcmgme is in the presence oi the extended neck poriioii which constitutes more or less si'ieee since the com bustllole filling material is generally disposed, ior the most part, in We bulbous porciorl of the cello. The neck portion is *slrus an unnecessary part insofar as the production oi the flesh of light is concerned. As a consequence, the size of the bulb is unnecessarily large, whereas the desideretum is to make flesh lamps as smell as possible for convenience in seemeporiailorr and use andior various other purposes.

One object of .my invention! is to provide a flesh lamp which, for a. given loulli size and a given factor of safety, will produce a. greater total light output, end il'lereiore a. grceier light output per unit of volume, than has heretofore been obtainable.

Another object of my invention is to provide a flash lamp which is more eficiem in the generation of light than flesh lorries hereiolore in use.

Still another object 03 my invention is to provide a flesh lamp with e Youilo of improved shape and of greaier strength and u- .formltv iahen the bulbs heretofore employee for flesh lamps.

A further object oiimy invention is to provide flash lamps with bulbs of relatively small size as compared to the bulbs heretofore in use for flash lamps oi comparable iota light output.

A s tll1 further object oi my invention is to provide a. flesh lamp of exceedingly smell size and or relatively high light cutout A feature oi the invention lo ose of sub siomiolly ovoidal emi mecielese "oiilo es coo ieiiier for the flesh lame, vii-iii coiiiliceilole materiel disposed uniformly jhlmlgl lll colly the wholeoi the space the or lion will appear from the oi species thereof and from the drawing in which Fig. 1 er eture flesh loimp compri u 2 is an elevation oi. e larger 5 comprising; my lnveriilori; 1' views illustrotlrig the see in the manufacture of the ice my invention; end I? mounted Within o. conceiiir siociiolly porobolololol eh Referring toihe zirevveog, izlie flesh cording to my invention coimorioee e celly cooled vilcreovri errvelorie oe cello etemiollv ovoldel or eiliyceolrlel me e. relatively short zoeclf; corlloir i extendingirom one errcl thereof. blllb'lflelsk portion ll l vice same is e loose ll of the o t or any oolrer suitable Woe. The loose lo preiemolv to the bulb rreci: by meeiic ceri'icro'e although other screens may be eiriplogvecl desired. The

ice-so is secured to the lirilb-vii'l-li its upper eelee oi crib .c. how

or rim abutting egems'i; the ovoiciel portion or the loulio. Thus we encloses ihe entire length of the neck portion ii and. ioeeiher with the intermediate "ring oi oerl'ieirb, servee to re liiloroe the sold meek pcrvioc. mills is cooled orl its inner or ouier surface, preferably both surfaces, with a coatingor o, suitable transparent varnish or lacquer to thereby prevent cracking of the bulb on charge flashing omi to render the cello substemiolly eileiierprool, are disclosed and claimed in coqoerlrlirig ecplioeiioir Serial No. 269,319? H. D. Bloke, filed April 21, 1939. The

' lmier coating is emailed over the entire inner surface oi the loulio including glie smell neck portion ll thereof. Through the use of em improved method of bulb sealing, the heroine of this firmer protective coating during such seeiine' operation is localized to a relatively small area oi the bulb neck adjacent the outer end thereof so than; the inner proieotive coating remains intact over the entire inner surface of the ovoidal portion of the/lmlo as well as the smell reversely curved portions joining the ovoidal and neck portions. As a result, the bulb i is better protected against cracking and shattering than is the case with the conventional pear-shaped bulbs used at present for flash lamps the inner lacquer coating of which is burned off the extended neck portion of the .bulb during the sealing-in operation thereby leaving an an preciable area oi? the bulb unprotected from the hot particles of combustible material.

Mounted substantially centrally within the ovoidal portion of the bulb ii? is a small filament I3 the ends of which are connected to leading-in wires l4, iii which extend through a stem it to the base l2. The filament it and adjacent portions of the leading-in wires i4, B5 are coated with a layer of a suitable fulminating substance ll to thereby form the primer or ignition means for the lamp. The fulminating material is pref= erably of the type disclosed and claimed in co ending United States application Serial No. 278,288, filed June 9, 1939, by George H. Merideth and assigned to the assignee of the present application. The Iulminating substance therein disclosed comprises a mixture or magnesium and zirconium metal powders and potassium perchlorate powder bonded together by a suitable binder such as nitro-cellulose.

A quantity of loosely arranged readily ebmbuswithin the ovoidal portion thereof and surround the ignition filament therein. The combustible material may consist of either a relatively thin foil or a filamentary \wire or ribbon of aluminum and/or magnesium. the filamentary wire or ribbon being the preferred form. The filamentary aluminum wire employed may be of the type produced by the method disclosed in my coending United States ap lication Serial No. 169,838; filed October 19, 1937.

Where wire is used as the combustible material, it is desirable to distribute the same as uniformly as-possible throughout the effective portion of the bulb to thereby obtain the most eflective combustion of the wire. To maintain such a uniform distribution of the wire at all times prior to the flashing of the lamp, I have found it advisable to positively secure the wire in place wi hin the bulb in a manner similar to that described and claimed in co-pending United States applicat on Serial No. 285.980, filed July 22, 1939, by John H. Cram and assigned to the assignee of the present invention. The securing of the wire in place within the bulb is accomplished accord ng to the present invention, by employing a thermoplastic lacouer for the protective coating on the inner wall of the bulb. Because of its thermoplastic nature. it is merely necessary to heat the lacquer coating to secure the wire in place within the bulb. Under the influence of heat, the thermoplastic lacquer becomes soft and tacky so that those portions of the wire which are in contact with the inner coating become embedded therein and are consequently stuck to the bulb wall upon hardening of the coating. In this manner the wire becomes attached to the inner wall of the bulb at a plurality of points, thus effectively maintaining the uniform spacing or distribution of the wire throughout the bulb and so insuring the most effective combustion of the wire-as well as uniform flash lamp characteristics. The heating and consequent softening of the thermoplastic inner lacquer'coating may be produced by the heat attending the sealingescapes in of the bulb or it may be produced by an en,- tirely separate heating operation.

As a result of the distribution of the combostible material throughout substantially the entire space within the bulb, the flash lamp according to the invention is more eillcient and uniform in the generation of light than flash lamps heretofore in use employing conventional pear-shaped bulbs. Because of the constricted neck portion of such pear-shaped bulbs and the glass stem extending therethrougli, the combustible material was disposed only in the bulbous or spherical portion of the bulb. Uonseqently, the combustionsupportmg gas within the bulb neck, because of its disposition at some distance from the location of the combustible material, was not eillciently utilized in the instantaneous reaction producing the hash of actinic light. In the lamps according to the invention, however, the combustible material is distributed uniformly throughout the entire volume of combustion-supporting gas within the bulb so that the entire quantity oi. gas eilectively assists in the combustion of the com bustible material and ensures the complete combustion thereoi'.

The bulb also contains a filling of oxygen or oxygen-containing gas at a suitable pressure for supporting the combustion of the combustible material IS. The pressure of this gaseous filling will vary, depending upon the type of gas employed, the size of the bulb, and the quantity and. type of combustible material therein. For the bulb sizes disclosed herein, and with oxygen being used as the combustion-supporting gas and pure aluminum as the combustible material, the pressure of the gaseous filling will vary up to 600 mm. of mercury or even close to one atmosphere.

The flash lamp shown in Fig. 2 differs from that shown in Fig. 1 only in that it is of larger size and is adapted to produce a flash of light of greater total output. Like the miniature lamp shown in Fig. 1, this larger lamp isalso provided with an ovoidal or ell psoidal bulb I0 and a base I! which in this case is of the screw-threaded type.

The substantially ovoldal or ellipsoidal shaped bulbs which are used in accordance with the invention as the container for flash lamps, can be made more uniformly and possess considerably greater strength than the conventional pearshaped bulbs heretofore in use. According to present-day methods of manufacturing lamp bulbs, the bulbs are formed from gobs or blanks of molten glass the central portion of which is a lowed to fall freely into a mold where it is then blown into the shape of the mold. The ovoidal shape of the bulbs according to the invention conforms very nearly to the shape of such a free falling gob of glass, much more so than the conventional pear-shaped bulb. Consequently, when the free falling gob of glass is finally blown out against the walls of the ovoidal shaped mold, very little deformation or stretching of the glass occurs. As a result, the walls of such ovoidal or ellipsoidal bulbs possess substantially the same uniform glass distribution which they possessed immediately prior to the blowing operation. There are no rapid changes in wall thickness, the inner and outer surfaces of the bulb wall having a smooth and uninterrupted curvature in the same direction, with no abrupt irregularities therein. In addition, such ovoidal blown bulbs do.not have thin maximum diameter side wall portions such as are characteristic of a pearseconds per cc. as the ilgurefor the miniature flash lamp reshaped or spherical-shaped blown bulb, nor do they have neck juncture portions as thin as those present in a spherical-shaped bulb, such thinner side walls and neck juncture portions constituting points of greater weakness in pear-shaped and spherical-shaped blown bulbs. In other words, the wall of the ellipsoidal bulb is-free of relatively sharp variations in thickness. It is for this reason, among others, that the ovoidal shaped bulb possesses greater strength than the pear-shaped bulb heretofore in use. Another reason for the greater strength of the ovoidal shaped bulb is the absence of the reversely curved portions present in the pear-shaped bulb, which portions join the neck and the bulbous portions of such bulbs. It is known that such reversely curved portions are a source of weakness in bulbs which are to be used for flash lamps, where considerable internal pressure is produced when the lamp is flashed. In the flash lamps according to the invention, the relatively small reversely curved portion joining the ovoidal bulb portion and the short neck portion is effectively reinforced by the surrounding base member l2, thus eliminating any weakness at such point.

As a result of their increased strength, the ovoidal shaped bulbs according to the invention can be safely loaded to a much higher degree than heretofore possible, thus enabling the use of bulbs of considerably smaller size for lamps of comparable light output. As far as known, the smallest flash lamps heretofore produced have employed bulbs the volumes of which amount to around 68 to '70 cc. My invention, however, has rendered it possible to produce flash lamps employing bulbs having considerably less volume than the smallest bulbs heretofore used, and in particular, less than 60 cc. Thus, the miniature flash lamp'shown in Fig. 1 employs a bulb having a volume of approximately 25 cc. Such a bulb may be safely charged with approximately 30 milligrams of filamentary aluminum wire or ribbon having a weight of approximately 1.14 milligrams per meter or thereabouts, together with a filling of' oxygen at a pressure or" approximately 600 mm. of mercury. Such a miniature flash lamp produces a flash of light averaging around 16,000 lumen seconds, which constitutes a relatively large amount of light for the size of bulb employed. As far as known, the highest light ouput per unit of bulb volume heretofore obtainable in flash lamps has been abount 400 lumen seconds per cc. However, the light output .per unit of bulb volume of the miniature lamp according to the invention amounts to approximately 640 lumen seconds per cc. Thus it will be seen that the miniature flash lamp comprising theinvention has a considerably higher light output per unit of bulb volume than has ever been ata pressure of approximately 500 mm. of mercury. Such a flash lamp produces a flash of light averaging around 50,000 lumen seconds. The light ouput per unit of bulb volume of this lamp therefore amounts to approximately 555 lumen While this figure is not as high ferred to above, nevertheless it is considerably higher thanthehighest light output per unit of volume (400 lumen seconds per cc.) heretofore obtainable. The reason, of course, for the increased light output per unit of volume of flash lamps accordingto the invention is the elimination of the extended neck portion present in the pear-shaped bulb, which constitutes more or less waste space, together with the increased loading of the bulb made possible by their increased strength as compared to the pear-shaped bulb.

As to the relative size and dimensions of the ovoidal bulbs according to the invention, the bulb ill of the miniature flash lamp shown in l. conforms substantially to an ellipsoid having a major axis A of about 1% inches and a minor axis 15 of about 15% inches. The ratio of length to width of such a dimensioned bulb is therefore approximately 1.2l. The neck portion it is of about /2 inch diameter and is of such a length the total overall length of the sealed bulb is ep= proximately 1% inches. The anal longitudinal cross-sectional or projected area above the bas= ing line 3-?) oil such a dimensioned bulb is approximately ll square cms. while the volume above the basing line is, as stated above, approx imately 25 cc. The ratio of the longitudinal pro jected area to the bulb volume is thereiore ap proximately one. The bulb l0 oi the larger= sized flash lamp shown in Fig. 2 is also of sub stantially ellipsoidal shape having a major axis C of about 2 inches and a minor axis D of about 1% inches. Accordingly, the ratio oi length to width oi such a dimensioned bulb is approximately 1.58. The neck portion ii is of such a length that the total overall length of the bulb is approximately 3H: inches. The axial ion gitudinal cross-sectlonal or projected area above the basing line b-b of such a dimensioned bulb is approximately 27.7 square .cms. while the-vol= ume above the basing line is, as stated above, approximately 90 cc. The ratio of the longitudinal projected area to the bulb volume is there-= fore approximately 030d.

Through the use of animproved method for sealing the bulb til, it has been possibl to practically eliminate theburning away of the inner protective lacquer coating on the bulb neck and adjacent portions oi! the bulb. Figs. 3, 4 and 5 illustrate the successive steps involved in the sealing of a bulb according to the invention. The bulb it, having its entire inner surface coated with a layer of protective lacquer and containing its filling l8 0! combustible material, is mounted in a vertical inverted position so that its neck porton H extends upwardly. The bulb is supported in this position partly by means of a combination support and heat shielding member or guard it which engages around the bulb neck at a point adjacent the junction of the bulb neck with the ovoidal portion of the bulb. A fllament mount, comprising the stem I6, leading-in wires It, IS, filament l3 and exhaust, tube 20,

is mounted above the bulb in an inverted position in alignment with the bulb neck, as shown in Fig. 3. This mount structure is then inserted into the bulb until the flange 2| of the stem tube It rests on the edge or rim of the bulb neck II, as shown in Fig. 2. Sharp pointed fires 22 are then directed onto the rim of the bulb neck II and the edge of the flange 2| on the stem tube until the glass softens and fuses together. The seal is then preferably stretched, in accordance with known practice, to remove internal strains therein, after which the bulb is fllled tipped off in the usual manner, as shown at 23' in Fig. Ellie base it is then cemented place on the bulb neck and the outer protective laesuer coating applied to the bulb. I

Instead of sealing the bulb fill while in. in verted position, it may be sealed while an up right position as is customary regular incandescent manufacture.

By the use or sharp-pointed sealing fires general heating of the bulb neck by the sealing fires is entirely obviated. The heat guard to shields the ovoidal portion or the bulb from the beat radiated by the sealing fires 22 and prevents the splashing of the latter onto sucli portions of the bulb, The combination oi the sharp-pointed fires 2% together with the heat shield i9 thus 10- calizes the heating or the glass to the bulb neck only and eflectively prevents the burning away of the inner protective lacquer coating on the ovoldal portiom of the bulb adjacent the bulb neck. In this manner, the inner protective lacquer coating is preserved over substantially the entire ovoidal portion of the bulb, i. e., the exposed portion of the bulb not enclosed by the base l2.

tected against cracking and shattering than the conventional pear-shaped bulb heretofore used in which the greater part of the extended and exposed neck portion was left unprotected because of the burning of! of the inner lacquer coating thereon during the sealing-in of the lamp. Although a portion of the inner lacquer coating on the neck portion ll of the bulb I0 is burned away by the heat attending the sealing-in operation, this loss in bulb strength and in protectlon against shattering is more than oflset by the added support or reinforcement given to the bulb neck by the enclosing base l2 which completely surrounds and engages the surface of the bulb neck. Thus, the combination of the inner protective lacquer coating over the entire inner surface of the ovoidal bulb portion, together with the reinforcing base entirely enclosing the bulb neck, results in a bulb of high strength and maximum protection against cracking and shattering. Accordingly, such bulbs can be safely loaded or charged to a higher degree than bulbs having a portion of their inner surface unprotected by a lacquer coating and unsupported by any external reinforcing means.

The exceptionally small size of the miniature flash lamp shown in Fig. 1 has made it possible to effectively employ therewith a substantially parabollc reflector 24 of a relatively small and practical size, as shown in Fig. 6, to thereby produce an intense concentrated beam of light. With such a combination, the major portion of the light output of the lamp is concentrated into the beam and therefore utilized in the taking of the picture, making it possible to take pictures of objects at relatively great distances. The miniature lamp II is mounted centrally about the focal point of the reflector 24, and because of its smallness in size (it more or less approximating a point source of light) the major portion of the reflected rays are redirected substantially parallel to, or at relatlvely small angles to the axis of the reflector.

As a result, the bulbs of flash lamps I made according to the invention are better propresent day photographic equipment.

, efiective utilization of the light outputof the lamp used in such a concentrating reflector has rendered possible the taking of excellent pictures at distances of feet and even more with Such e3:- traordinary results have been heretofore possible only with tire aid of relatively large-sized, and therefore impractical, reflectors.

Where it is desirable to obtain a greater light output than that obtainable from one flash lamp only, a. number of lamps according to the inventlon may be grouped together in a large reflector and simultaneously flashed. In this manner, a greater utilization of the light output from the several lamps is obtained than is possible from one large lamp designed to give the same light output as the combined total output of the several lamps. The reason for this is that by combining the light output of the several lamps, the peaks of the individual lamps average up so that the peak of a. group of lamps occurs with more uniformity at the desired time instant when the camera shutter is at the mid-point of its exposure than is the case with a large single lamp designed to give alight output equal to the combined total light output of the several lamps.

What I. claim as new and desire to secure by Letters Patent of the United States is:

1. A flash lamp of the type comprising a sealed blown glass bulb containing a charge of combustible flash material, in which the said bulb is of ellipsoidal shape, the wall of said ellipsoidal bulb being substantially free of relatively sharp variations in thickness and having a smooth curvature in the same direction throughout its longitudinal cross-sectional periphery.

2. A flash lamp of the type comprising a sealed blown glass bulb containing a charge of combustlble-flash material and a base secured to said bulb, wherein the said bulb is of ellipsoidal shape with a short tubular neck portion at one end, the

- wall of said ellipsoidal portion of the bulb being substantially free of relatively sharp variations in thickness and having a smooth curvature in the same direction throughout its longitudinal cross-sectional periphery, and the said base entlrely encloses and reinforces the neck portion of said bulb so that only the ellipsoidal portion is exposed.

3. A flash lamp comprising a blown glass bulb of ellipsoidal shape having a short tubular neck portion at one end thereof, the wall of the ellipsoidal portion of said bulb being substantially free of relatively sharp variations in thickness and having a smooth curvature in the same direction throughout its longitudinal cross-sectional periphery, a glass stem extending into said bulb through said neck portion and fused at its outer end to the end of said bulb neck portion, electrical ignition means in said bulb supported by said stem, a charge of combustible flash material in said envelope arranged to be ignited by said lgnitlon means. and a base surrounding the entire bulb neck portion and firmly secured thereto to reinforce it so that only the ellipsoidal portion of the bulb is exposed.

MARVIN PIPKIN. 

